epic: make Dispatch lanes configurable

[joryirving]

Goal

Make Dispatch lanes configurable instead of hardcoding the current built-in lane set.

Today Dispatch assumes a fixed lane model in several places. That works for the current deployment, but it makes the project harder to reuse for other agent/model setups. A user should be able to run Dispatch with one claimable lane, two lanes, three lanes, or another custom set without changing source code.

Desired model

Dispatch should support lane profiles configured at runtime or from repo config, for example:

lanes:
  - id: default
    title: Default
    claimable: true
  - id: backlog
    title: Backlog
    claimable: false

or:

lanes:
  - id: local
    title: Local
    claimable: true
  - id: cloud
    title: Cloud
    claimable: true
  - id: frontier
    title: Frontier
    claimable: true
  - id: backlog
    title: Backlog
    claimable: false

The shipped default should preserve current behavior for existing installs.

Non-goals

• Do not change external workflow repos in this epic.
• Do not require any specific agent names.
• Do not require any specific model/provider names.
• Do not remove existing lane data.
• Do not break current normal/escalated/backlog deployments.

Design principles

• Lanes are Dispatch-owned routing metadata.
• backlog is special only because it is not claimable worker work.
• Claimable lanes should be data-driven.
• Single-lane deployments must be valid.
• Queue APIs should continue to filter by lane when a lane is requested.
• Existing installs should continue to work without new config.

Child issues

• feat: add lane configuration model and defaults #382
• refactor: replace hardcoded lane constants with lane helpers #383
• feat: support configurable lanes in agent queue APIs #384
• feat: make issue reconciliation use configurable lanes #385
• feat: render board and lane filters from lane configuration #386
• feat: support migration-safe custom lane deployments #387
• docs: document configurable lane setups #388

Acceptance criteria

• Dispatch can run with the current default lanes without behavior changes.
• Dispatch can run with one claimable lane plus backlog.
• Dispatch can run with three claimable lanes plus backlog.
• Queue APIs respect the configured lane set.
• UI renders lane choices from config instead of hardcoded assumptions.
• Reconciliation/classification never writes a lane not present in config.
• Tests cover current default lanes and at least one custom lane configuration.
• Documentation explains how to configure lanes.

Validation

• npm run lint
• npm run typecheck
• npm run test
• npm run build

[itsmiso-ai]

All acceptance criteria for the configurable lanes epic are now satisfied.

Completed child issues:

• feat: add lane configuration model and defaults #382 — foundation for configurable lanes
• refactor: replace hardcoded lane constants with lane helpers #383 — replaced hardcoded lane constants with lane helpers (PR refactor: replace hardcoded lane constants with lane helpers #430)
• feat: support configurable lanes in agent queue APIs #384 — configurable lanes in agent queue APIs (PR feat: support configurable lanes in agent queue APIs #431)
• feat: make issue reconciliation use configurable lanes #385 — issue reconciliation uses configurable lanes (PR feat: make issue reconciliation use configurable lanes #432)
• feat: render board and lane filters from lane configuration #386 — render board and lane filters from configuration (PR feat: render board and lane filters from lane configuration #433)
• feat: support migration-safe custom lane deployments #387 — migration-safe custom lane deployments (PR feat: support migration-safe custom lane deployments #434)
• docs: document configurable lane setups #388 — documented configurable lane setups (PR docs: document configurable lane setups #435)

Verified:

• Default lanes work without behavior changes
• Single claimable lane + backlog is supported
• Three claimable lanes + backlog is supported
• Queue APIs respect configured lane set
• UI renders lanes from config
• Reconciliation never writes unconfigured lanes
• Tests cover default and custom configurations
• Documentation explains configuration in docs/configurable-lanes.md

Closing this epic.